The invention relates to a reflection reducing coating. With the solution according to the invention the reflection of light impinging upon the surface of substrates can be effectively and largely decreased, which is desirable for many cases of application, in particular for many optical elements (lenses, windows and prisms etc.) or opto-electronic elements, and for spectacle glasses as well. The coating can be particularly advantageously employed for the reflectance decrease in the visual spectral range.
For a plurality of applications, and spectacle glasses are to be explicitly mentioned, it is also required to provide a respective xe2x80x9cantireflex coatingxe2x80x9d having a high abrasion resistance.
In the past, synthetic material has also enforced as material for optical elements and spectacle glasses, in particular due to the manufacturing cost and the lower density in comparison with glasses.
Although the synthetic material has equivalent optical characteristics with respect to the glasses used until now, however, it provides a Substantially lower scratch resistance such that with the mechanical influences having an abrasive effect the surfaces become damaged and the optical performance is deteriorated.
For optical components, and in particular spectacle glasses abrasiveproof and reflection reducing surfaces are required which can only be achieved by means of the respective coatings.
In accordance with the International Standard ISO 9211-02, for example, such coatings have to meet a sufficient wiping resistance also during cleaning processes which are performed with cotton clothes or rubber.
In particular with the spectacle glasses hard layers having a thickness of several micrometers, and thereupon an additional reflection reducing coating are deposited.
Such hard layers can be manufactured by a layer of lacquer and the subsequent vacuum evaporation of a reflection reducing coating such as described by W. Kxc3x6ppen and E. Kampmeyer in DOZ 2(1995), pp. 22 to 26.
The generation of hard layers by means of plasma polymerization originates from J. Bxc3x6tschi, F. Thieboud, and is mentioned in DOZ 10 (1992), pp. 26 to 27; and by D. Giessner in NOJ 5 (1995), pp. 62 to 64 with respect to the vacuum evaporation of such hard layers, wherein the publication last mentioned is a matter of organically modified quartz layers. Subsequently, with depositing such hard layers again it is necessary to deposit the reflection reducing cover layer by means of well-known CVD and PVD processes, respectively.
The same demands as with respect to other substrate materials are made in particular on thermoplastic polymers such as poly(methyl methacrylate), polycarbonate and such other synthetic materials, wherein up to now accordingly suitable coatings are obtained in a wet-chemical manner or by means of vacuum evaporation, and a combination of such coating methods, respectively. Thus, a wet-chemical layer with well-known coating methods is an additional time consuming and expensive manufacturing step which is separated from the procedure step of forming the reflection reducing layer. For precision optics having very irregularly formed and greatly curved surfaces, and with small sized optical elements such methods are not suitable. With a reflection reducing coating which has been deposited on a relatively thick, more abrasiveproof hard layer an additional waviness of the spectral reflection of the total layer system occurs due to interference action with different refractive indices of the substrate material and hard layer.
For broadband reflection reducing coatings which for example cover the wavelength range of the visual light, two to six individual layers are required. With the well-known change layer systems a temperature rise of the substrate temperatures can occur. Temperatures can be achieved which are above of critical softening temperatures (e.g. 80 to 110xc2x0 C. with acrylates) of the substrate material. Then, the temperature rise substantially occurs by the vaporization of the layer material having a high refractive index.
Therefore, it is an object of the invention to provide a reflection reducing coating on a Substrate which can be deposited upon any substrates without occurring an unacceptable temperature rise during depositing.